Cervical cancer is one of the common neoplasms of the female genital tract. Cervical cancer is the second malignancy in women worldwide and is one of the leading causes of women death in the third world. Early diagnosis of abnormal cells in the cervix prevents deterioration into fully cervical cancer and thus reduces morbidity and mortality. The pre-cancerous state is called Squamous Intraepithelial Lesion (SIL), and has two grades: low grade SIL and high grade SIL.
The uterine cervix is very good for screening purposes for several reasons. First, the tumoral changes occur in a specific area, called the transitional zone, around the “external of” (opening of the cervical canal into the vagina). Second, these are slow growing tumors. Third, this area is external in the body and can be easily analyzed by a Gynecologist.
The current screening method, called a Pap smear, has been used for decades. During a Pap smear, a large number of cells, obtained by scraping the cervical epithelium, are smeared onto a slide, or into a liquids tube, which is then fixed and stained for cytologic examination. Unfortunately, the Pap smear is unable to achieve a concurrently high sensitivity and high specificity due to both sampling and analysis errors. Estimates of the sensitivity and specificity of Pap smear screening range from 11-99% and 14-97%, respectively. As used herein, the term sensitivity is defined as the correct classification percentage on pre-cancerous tissue samples, and the term specificity is defined as the correct classification percentage of normal tissue samples. According to the National Cancer Institute (NCI), about 55 million Pap tests are performed each year in the USA. Of these, approximately 3.5 million are abnormal and require medical follow-up. Most of the abnormal tests are in fact falsely indicative of SIL.
Additionally, analyzing Pap smears is extremely labor intensive and requires highly trained professionals. A patient with an abnormal Pap smear indicating the presence of SIL needs to then undergo a diagnostic procedure called colposcopy, which involves colposcopic examination, and if needed biopsy and histology confirmation of the clinical diagnosis. Extensive training is necessary in order for a practitioner to perform colposcopy and its diagnosis accuracy is variable and limited, even in expert hands. Moreover, diagnosis is not immediate.
Thus, it would be desirable to provide a method for early detection of cervical cancer with improved specificity and sensitivity, which reduces the required skill level of the practitioner interpreting the results and shortens the diagnosis period.
One “in vivo” method of detection is Electrical Impedance Spectroscopy (EIS), which indicates the condition of the tissue by the change of impedance with frequency. Disadvantageously, EIS has positive predictive value (PPV) of only 72% and is an expensive process.
Thus, it would be desirable to provide a method and apparatus for detection of cervical pre-cancer that provides greater sensitivity and selectivity than prior art techniques. Additionally, it would be desirable to provide such a technique which is also cost effective.